First, your life's not over. You're 17. You've barely gotten started.
That said, there are a lot of possible things that may be going on. The first is a food intolerance, as 82brandy mentioned. Second, what about water (actual, true to life H2O, not teas or sodas)? Do you drink enough. If you eat enough fiber (are you eating enough fiber?) and you don't drink enough water, gas is inevitable. Third, have you tried a colonic cleanse? Fourth, what's your diet like? Maybe you just have a sensitive stomach and need to watch that you're not eating the wrong foods. Have you noticed patterns? That's the first step.
what do you eat? you need to go see an allergy doctor. how about lactose intolerance?
try cutting dairy out of your diet. if that doesnt work it could be something else. dont giveup. you're life isnt over. food allergies are serious and likely a cause. again, what do you eat on a regular basis?